Linux Kernel up to 7.1.4 hfsplus fs/hfsplus/bnode.c hfsplus_bnode_find rec_off uninitialized variable

Summaryinfo

A vulnerability has been found in Linux Kernel up to 7.1.4 and classified as critical. Affected by this issue is the function hfsplus_bnode_find of the file fs/hfsplus/bnode.c of the component hfsplus. This manipulation of the argument rec_off causes uninitialized variable. This vulnerability is registered as CVE-2026-80656. The attack needs to be launched locally. No exploit is available.

Detailsinfo

A vulnerability classified as critical was found in Linux Kernel up to 7.1.4. Affected by this vulnerability is the function hfsplus_bnode_find of the file fs/hfsplus/bnode.c of the component hfsplus. The manipulation of the argument rec_off with an unknown input leads to a uninitialized variable vulnerability. The CWE definition for the vulnerability is CWE-457. The code uses a variable that has not been initialized, leading to unpredictable or unintended results. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: hfsplus: Add a sanity check for btree node size Syzbot reported an uninit-value bug in [1] with a corrupted HFS+ image, during the file system mounting process, specifically while loading the catalog, a corrupted node_size value of 1 caused the rec_off argument passed to hfs_bnode_read_u16() (within hfs_bnode_find()) to be excessively large. Consequently, the function failed to return a valid value to initialize the off variable, triggering the bug [1]. Every node starts from BTree node descriptor: struct hfs_bnode_desc. So, the size of node cannot be lesser than that. However, technical specification declares that: "The node size (which is expressed in bytes) must be power of two, from 512 through 32,768, inclusive." Add a check for btree node size base on technical specification. [1] BUG: KMSAN: uninit-value in hfsplus_bnode_find+0x141c/0x1600 fs/hfsplus/bnode.c:584 hfsplus_bnode_find+0x141c/0x1600 fs/hfsplus/bnode.c:584 hfsplus_btree_open+0x169a/0x1e40 fs/hfsplus/btree.c:382 hfsplus_fill_super+0x111f/0x2770 fs/hfsplus/super.c:553 get_tree_bdev_flags+0x6e6/0x920 fs/super.c:1694 get_tree_bdev+0x38/0x50 fs/super.c:1717 hfsplus_get_tree+0x35/0x40 fs/hfsplus/super.c:709 vfs_get_tree+0xb3/0x5d0 fs/super.c:1754 fc_mount fs/namespace.c:1193 [inline]

It is possible to read the advisory at git.kernel.org. This vulnerability is known as CVE-2026-80656 since 08/26/2026. The exploitation appears to be easy. Attacking locally is a requirement. The exploitation requires an enhanced level of successful authentication. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/28/2026).

Upgrading to version 7.1.5 eliminates this vulnerability. Applying the patch 306265eb9384d2c224f1b14d83a29323f0eab6d1/3f95e2661574ff13f099dd13456751933c280628 is able to eliminate this problem.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.1.0
• 7.1.1
• 7.1.2
• 7.1.3
• 7.1.4

License

• open-source

Website

• Vendor: https://www.kernel.org/

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